1. Field of the Invention
The invention relates to an exchangeable-type disk apparatus, such as CD-ROMs, DVDs, MOs and removable HDDs, and more particularly to a disk-type reproducing apparatus in which the influence of unbalanced vibration of a disk is reduced.
2. Description of the Related Art
Most software for computers has been distributed in the form of CD-ROMs, and in order to reduce the installation time for such CD-ROMs and to afford comfortably enjoying games and so on, it has been required to increase the data transfer speed. To achieve this, it is necessary to turn (spin) a disk at high speed. A major problem encountered in this case is an increase in vibrations due to unbalance of the disk. In order to reduce the vibrations, Japanese Patent Unexamined Publication No. 10-083622 has proposed a method in which support legs of a rotating system are made sufficiently flexible to set the resonance frequency of the support system to a lower level than an operating revolution frequency, and the apparatus is operated in such overcritical condition that a balancer mounted in the rotating system corrects unbalance of the disk.
In the above prior art technique, the balancer comprises a spherical body (ball), and such spherical body rolls in a groove provided at a center of rotation to correct the unbalance. However, when the disk spins at a speed near the resonance frequency of the rotating system, the ball unsteadily moves in the rolling groove to cause unstable vibrations, thus producing vibrations and noises, and furthermore there has been a problem that servo for a disk reading system does not work to make reading of information impossible.
It is an object of the invention to provide a disk apparatus which eliminates a phenomenon that servo is made out of control by unstable vibrations developed when a disk is spun at a speed near the resonance frequency of the rotation support system of the above unbalance correcting mechanism.
The above object of the invention can be attained by positioning a ball in a position of correction while once increasing revolutions of a disk above the resonance frequency of the rotation support system when the disk is started to spin, and thereafter decreasing the revolutions to execute actuation of the servo.